Why North Carolina’s electric co-ops are turning to grid batteries

In July 2022, a fierce summer storm rocked Wake Electric, a North Carolina cooperative serving nearly 60,000 households and other customers from the dense suburbs of Raleigh, the state capital, to rural areas along the Virginia border and in the coastal plain. Wind downed lines and knocked out power for thousands for over seven hours.

“It was one of these very difficult outages where we had a line laying across a road,” said Don Bowman, the co-op’s senior vice president and assistant general manager. ​“We had to coordinate a lot of activities, and it took us a while to get this power back on.”

But Eagle Chase, a small housing community equipped with a propane-fueled generator and a 1-megawatt Tesla battery pack, was almost completely unscathed. The devices form a microgrid that can function without the co-op’s larger distribution system of poles and wires.

“The success story,” Bowman said, ​“is the Eagle Chase development saw an outage of less than about 58 milliseconds.”

The Eagle Chase battery is among three storage systems in Wake Electric’s territory. The second, in Wake Forest, is a 1-megawatt-hour battery paired with a 500-kilowatt solar farm; its purpose is to dispatch solar electrons when the sun doesn’t shine. The third, a 5-megawatt battery located at the co-op’s main substation, stores power that can be discharged when supplies are constrained and electricity prices are high.

The systems illustrate three key advantages of battery storage, Bowman said: providing resiliency, increasing the reliability of renewable energy, and responding to periods of high demand.

“We have three systems, and I think that we check all three of those boxes differently with each of the projects,” he said. 

“What these battery systems have been able to do is really save folks money while increasing resilience, and helping with reliability sort of across the footprint,” said Rob Greskowiak, chief commercial officer for Lightshift Energy, a storage developer that has worked with several co-ops outside North Carolina, including in neighboring Virginia. ​“It’s really an economic story.”

Money isn’t the only motivator. Co-ops often serve far-flung corners of the state, where an investor-owned utility like Duke Energy would earn a meager profit. Many of these areas — from rugged mountains to fragile barrier islands — are also prone to outages from extreme weather.

That’s why almost decade ago, Tideland Electric Member Corp. set up the state’s first cooperative-run microgrid on Ocracoke Island — complete with 62 solar panels, a battery pack, and a diesel generator. The system kept the power on for island residents in the summer of 2017, after a construction crew accidentally severed a transmission line to the mainland.

“The solar worked,” Heidi Smith, a Tideland co-op manager, said back then. ​“The Tesla batteries were able to add power to the system.”

North Carolina’s co-ops also have set a target of zeroing out their carbon emissions by midcentury, though, unlike Duke, they’re not required to by law.

“It’s in our mission statement to constantly be moving toward cleaner energy solutions,” Bowman of Wake Electric co-op explained.

The benefits and costs of the individual battery systems can be spread out among the co-ops and their millions of customers, since all these storage devices are managed by the North Carolina Electric Membership Corp.

“Having all of these assets is wonderful,” the corporation’s Hall said. ​“But if you can’t aggregate them and utilize them when they’re needed, then you’re not really bringing to bear the value of them.”

That means calling on the storage assets when high demand sends electricity prices soaring or dispatching them during extreme weather events to enhance reliability. 

“I sound like I’m tooting our horn, and I am,” Hall said. ​“We’ve built one of the most innovative and capable [distributed energy resource management] systems in the country.” 

“I don’t call it a virtual power plant, because it sounds very financial, economic,” he added. ​“Our systems are grounded in reliability.”

Still, not every move made by the state’s co-ops has been in lockstep with the clean energy transition. North Carolina Electric Membership Corp. is pursuing a large new gas-generation plant in Person County in conjunction with Duke and already owns two single-cycle, peaking gas plants outright. It’s also made a long-shot bid to the Federal Energy Regulatory Commission that, if successful, could upend how transmission upgrades are paid for and stall new solar from coming onto the grid.

The split screen just reinforces that batteries are not, for many adopters, first and foremost about curbing carbon emissions.

“North Carolina can be viewed as a leader in this space, but I think it’s important to reiterate that it’s not because of sustainability goals or clean energy goals,” Greskowiak said. ​“The economic case for battery storage is only going to grow. The rest of the country is catching up.”